U.S. patent application number 16/635185 was filed with the patent office on 2021-02-25 for method for producing cured polymeric skins.
The applicant listed for this patent is ALDINO ALBERTELLI. Invention is credited to ALDINO ALBERTELLI.
Application Number | 20210053300 16/635185 |
Document ID | / |
Family ID | 1000005236562 |
Filed Date | 2021-02-25 |
United States Patent
Application |
20210053300 |
Kind Code |
A1 |
ALBERTELLI; ALDINO |
February 25, 2021 |
METHOD FOR PRODUCING CURED POLYMERIC SKINS
Abstract
This invention relates to the production of cured polymeric skin
materials. In particular, the invention relates to methods and
substrates for the production of skin materials, for example, for
use in building, furniture, and as architectural components for
example in roofing materials such as roofing tiles, or for brick
wall effect materials.
Inventors: |
ALBERTELLI; ALDINO; (DUBLIN,
IE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALBERTELLI; ALDINO |
DUBLIN |
|
IE |
|
|
Family ID: |
1000005236562 |
Appl. No.: |
16/635185 |
Filed: |
July 31, 2018 |
PCT Filed: |
July 31, 2018 |
PCT NO: |
PCT/GB2018/052181 |
371 Date: |
January 30, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29K 2105/0872 20130101;
C08J 5/18 20130101; B29K 2267/00 20130101; B32B 2419/06 20130101;
B29C 70/54 20130101; B29C 70/465 20130101; C08J 2361/04 20130101;
B32B 2262/101 20130101; B32B 5/022 20130101; B29C 2035/0855
20130101; C08J 5/121 20130101; E04F 13/142 20130101; B29K 2061/04
20130101; B29L 2031/108 20130101; B29K 2105/251 20130101; B32B 5/16
20130101; B29C 35/0805 20130101; B29K 2105/0863 20130101; B32B
27/14 20130101; B32B 27/12 20130101; B32B 2264/1021 20200801; B32B
27/42 20130101 |
International
Class: |
B29C 70/46 20060101
B29C070/46; C08J 5/18 20060101 C08J005/18; C08J 5/12 20060101
C08J005/12; B29C 70/54 20060101 B29C070/54; B29C 35/08 20060101
B29C035/08; B32B 5/16 20060101 B32B005/16; B32B 5/02 20060101
B32B005/02; B32B 27/12 20060101 B32B027/12; B32B 27/14 20060101
B32B027/14; B32B 27/42 20060101 B32B027/42; E04F 13/14 20060101
E04F013/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2017 |
GB |
1712320.9 |
Claims
1-48. (canceled)
49. A method of forming a cured polymeric skin, the method
comprising: providing a sheet-form curable material; providing a
substrate in particulate form; contacting the particulate substrate
with a first surface of the sheet-form curable material; pressing
the particulate substrate to the sheet-form curable material; and
at least partially curing the sheet-form curable material to form a
skin, wherein the configuration of the substrate is such that gas
and/or vapour can be displaced from the pressing region, and a
portion of the sheet-form curable material flows into the
particulate substrate.
50. The method according to claim 49, wherein the particulate
substrate comprises a plurality of interstitial spaces between the
particles such that the sheet-form curable material can flow into
the particulate substrate.
51. The method according to claim 50, wherein the interstitial
spaces have a diameter in the range of 0.25 to 5 mm.
52. The method according to claim 49, wherein the particulate
substrate comprises one or more particulate materials selected from
sand, gypsum, graphite, calcium carbonate, hydrated organic salts,
ceramic materials, clay materials, and metal oxides.
53. The method according to claim 49, wherein the particulate
substrate comprises one or more materials susceptible to
electromagnetic radiation.
54. The method according to claim 49, wherein the sheet-form
curable material comprises a thermosetting material.
55. The method according to claim 54, wherein the sheet-form
curable material has a thickness of 0.3 to 50 mm.
56. The method according to claim 54, wherein the thermosetting
material comprises: uncured phenolic resin; filler; and a catalyst
in an amount of less than 1 wt. % relative to the content of
phenolic resin, wherein the filler is present in a ratio of filler
to uncured phenolic resin in an amount of 3:1 and greater, and
further wherein the filler comprises a transition metal hydroxide
and/or aluminium hydroxide in a ratio of metal hydroxide to uncured
phenolic resin in an amount of 2:1 to 3:1.
57. The method according to claim 56, wherein the catalyst is
present in an amount of less than 0.5 wt. % relative to the content
of the uncured phenolic resin.
58. The method according to claim 56, wherein the transition metal
or aluminium hydroxides are of formula M(OH).sub.3, wherein M is a
metal.
59. The method according to claim 56, wherein the filler is a
particulate solid which is insoluble in the thermosetting
material.
60. The method according to claim 49, wherein the sheet-form
curable material further comprises fibers, wherein the fibers are
added to the uncured material in a ratio of resin to fiber of 6:1
to 1:3.
61. The method according to claim 56, further comprising the step
of providing one or more masonry tiles, the masonry tiles being
applied to the sheet-form curable material prior to contacting with
the particulate substrate.
62. The method according to claim 61, wherein masonry tiles have a
depth in the range of from 3 to 30 mm.
63. The method according to claim 49, further including a step of
applying the sheet-form curable material to a mould.
64. The method according to claim 63, wherein the mould is in the
form of a template defining a pattern to be formed by the masonry
tiles.
65. The method according to claim 49, further including a step of
providing a veil on a second surface of the sheet-form curable
material between the sheet-form curable material and a surface of
the mould.
66. The method according to claim 49, further including a step of
contacting a particulate surface material with a second surface of
the sheet-form curable material and pressing the sheet-form curable
material and the surface material.
67. The method according to claim 49, wherein after at least
partially curing, at least a part of the particulate material is
exposed at a surface of the sheet-form material.
68. The method according to claim 49, wherein the curing step
comprises heating the sheet-form curable material to a temperature
greater than 100.degree. C.
69. The method according to claim 49, wherein the particulate
substrate is heated prior to contact with the sheet-form curable
material.
70. The method according to claim 53, further including a step of
irradiating the particulate substrate with electromagnetic
radiation to increase the temperature of the substrate.
71. The method according to claim 61, the method comprising:
optionally providing a template on a press; providing a sheet-form
curable material on the press; arranging masonry tiles on a surface
of the sheet-form curable material to form a pattern; applying a
particulate substrate such that it covers at least any remaining
surface area of the sheet-form material to the height of the
masonry tiles; pressing the sheet-form curable material to the
substrate; and at least partially curing the sheet-form curable
material, wherein the configuration of the particulate substrate is
such that gas and/or vapour can be displaced from the pressing
region, and a portion of the sheet-form curable material flows into
the particulate substrate.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the production of cured polymeric
skin materials. In particular, the invention relates to methods and
substrates for the production of skin materials, for example, for
use in building, furniture, and as architectural components for
example in roofing materials such as roofing tiles, or for brick
wall effect materials.
BACKGROUND TO THE INVENTION
[0002] Panels and other elements used in building have
traditionally been made of natural materials. For example, doors
and panels for buildings and furniture have traditionally been made
from wood. Other walls and panels have been made or brick or stone.
Roofing tiles have traditionally been made from clay, slate or
terracotta.
[0003] There is now a trend for building elements and other
products which would traditionally have used natural products to be
made from "non-natural" or synthetic products, for example plastics
materials. Such modern materials have many chemical, physical and
cost advantages compared with traditional materials. Foam resin
skin panels of the kind comprising a foam resin layer and a
polymeric cured skin, for example, a cellular foam with an sheet
moulding compound (SMC) skin surface are being employed
increasingly in the building, decorating and furniture industries
because of the wide range of useful properties achievable.
Increasingly surface effects have been added to the skin material
to form, for example, simulated surfaces such as a simulated stone
surface, or a brick wall.
[0004] In a known method of forming panels, the panels comprise a
pair of outer skins and an internal foam core. The skin or skins
and the foam core are formed separately and may then be bonded
together, usually by means of an adhesive. In known systems, the
skins may be formed by compression moulding of a SMC. The SMC
includes a thermosetting resin, for example a polyester resin,
together with reinforcing fibres, for example glass fibres.
[0005] In known methods the SMC is folded to form a block of charge
and placed into a preheated moulding cavity. The mould is closed
and pressure is applied to press the moulding compound so that it
spreads to all parts of the mould. Heat and pressure is applied
until the moulded material has cured.
[0006] There are disadvantages associated with forming the SMC
skins using such a method. For example, the SMC needs to be folded
to form a block in the mould cavity. This is because air trapped in
the mould cavity and gases formed during the curing reaction need
to be released during the moulding operation. Further, high
pressure is required to affect the moulding; pressures of 1000 to
1200 tonnes per m.sup.2 are not unknown. Another disadvantage
associated with known methods of forming cured skins is that the
skin damages the mould whilst curing so that it cannot be reused.
Specifically, the skin stretches the mould during curing, or if a
surface decoration is present, this may scratch the mould and
causes damage to it--both of these disadvantages prevent the mould
being reused.
[0007] To try and alleviate these problems it was found (for
example in WO2009/044169 and WO2010/046699) that by contacting the
curable material with a solid cellular substrate, gas or vapour
that might otherwise remain and/or build up in the pressing region
(i.e. the area where the surface of the substrate and a sheet-form
curable material are being pressed together) could be removed by
flowing into the cells of the solid substrate and as such the
pressure required to form the composite product significantly
reduced.
[0008] Known solid substrates have an open-celled cellular
structure, which allows movement of the gases away from the
pressing region whilst retaining dimensional stability within the
mould. However, these methods are limited in that only certain
materials may be used as the substrate, i.e. only materials which
have a suitable open cell structure to allow air and/or other
gasses to be removed. Currently used solid substrates are
substantially rigid materials, for example self-supporting foams
which are resilient to load and do not collapse under moderate
pressure. These foams generally have cell sizes in the range of 0.5
mm to 5 mm. The sheet-form curable material (for example SMC) bonds
to the substrate during curing. This causes difficulties if the
skin is to be used independently of the foam substrate. Known
methods machine the cured skin off the foam surface which leads to
damage of the skin surface.
[0009] In the processes described above, a large amount of
materials are required in order to make the cured skin, some of
which are not present in the final product and cannot be reused,
for example the substrate material. This creates a large cost
associated with the method.
[0010] There remains a need in the art for an alternative process
for the production of a polymeric cured skin, in particular an SMC
containing polymer skin material which seeks to alleviate or reduce
one or more of the issues discussed above.
SUMMARY OF THE INVENTION
[0011] According to the present invention, there is provided a
method of forming a cured polymeric skin, the method comprising:
[0012] providing a sheet-form curable material; [0013] providing a
substrate in particulate form; [0014] contacting the particulate
substrate with a first surface of the sheet-form curable material;
[0015] pressing the particulate substrate to the sheet-form curable
material; and [0016] at least partially curing the sheet-form
curable material to form a skin, wherein the configuration of the
substrate is such that gas and/or vapour can be displaced from the
pressing region, and a portion of the sheet-form curable material
flows into the particulate substrate.
[0017] The present invention also provides a method of forming a
cured polymeric skin, the method comprising: [0018] optionally
providing a template on a press; [0019] providing a sheet-form
curable material on the press [0020] arranging masonry tiles on a
surface of the sheet-form curable material to form a pattern;
[0021] applying a particulate substrate such that it covers at
least any remaining surface area of the sheet-form material to the
height of the masonry tiles (and preferably also the masonry
tiles); [0022] pressing the sheet-form curable material to the
substrate; and [0023] at least partially curing the sheet-form
curable material, wherein the configuration of the particulate
substrate is such that gas and/or vapour can be displaced from the
pressing region, and a portion of the sheet-form curable material
flows into the particulate substrate.
[0024] Also provided in accordance with the present invention is a
skin formed by a method disclosed herein.
[0025] Such polymeric skins may comprise at least a portion of the
particulate substrate material present on a surface of the skin;
and optionally a particulate material is present on a second
surface of the skin.
[0026] Additionally, such polymeric skins may comprise one or more
masonry tiles present on a surface of the skin as well as at least
a portion of the particulate substrate material.
[0027] Also provided is the use of a particulate material in a
method of the present invention.
[0028] The methods of the present invention may be advantageous in
a number of respects. For instance, it has surprisingly been found
that a particulate material can be used as a pseudo-substrate
(hereinafter referred to as a substrate) to remove gas or vapour
from the pressing region.
[0029] In addition, the particulate material can be easily removed
from the polymeric cured skin, thus enabling a facile way to obtain
the skin material independently of a substrate. This also provides
the added advantage of a more efficient process as the step of
machining the skin off the substrate is no longer necessary. The
process of the present invention takes less time, and costs less
compared to known processes.
[0030] A particular advantage of the present invention is that
remaining particulate material may be reused after the polymeric
cured skin has been removed therefrom. This lowers the overall cost
of the process. The use of the reusable particulate substrate which
can be brushed off the sheet-form curable material allows for key
method steps in known methods to be avoided meaning that the
present process take less time and cost less money whilst still
alleviating the problem of gas build up in the pressing region.
[0031] A still further advantage of the present invention is that
the particulate material may be pressed into the sheet-form curable
material such that a textured surface appears on a surface of the
skin once cured. In some instances, this removes the need to apply
a separate layer of particulate material on a second surface of the
sheet-form curable material during production.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 shows an example of a method of forming a cured
polymeric skin product;
[0033] FIG. 2 shows an example of a method of forming a cured
polymeric skin with a surface effect;
[0034] FIG. 3 is an exploded diagrammatic view of a process in
accordance with the present invention;
[0035] FIG. 4 is a diagrammatic view of the layers as applied in
the process of FIG. 3; and
[0036] FIG. 5 is a diagrammatic cross-sectional view of the cured
skin produced in the process of FIGS. 3 and 4.
DESCRIPTION OF THE INVENTIONS
[0037] As discussed above, the present invention provides a method
of forming a cured polymeric skin, the method comprising: [0038]
providing a sheet-form curable material; [0039] providing a
substrate in particulate form; [0040] contacting the particulate
substrate with a first surface of the sheet-form curable material;
[0041] pressing the particulate substrate to the sheet-form curable
material; and [0042] at least partially curing the sheet-form
curable material to form a skin, wherein the configuration of the
substrate is such that gas and/or vapour can be displaced from the
pressing region, and a portion of the sheet-form curable material
flows into the particulate substrate.
[0043] By using a particulate substrate, air and gas produced
during the pressing step can pass through interstitial spaces
between particles so that the risk of air and gasses leading to
deformities in the skin are reduced.
[0044] By particulate, it is meant that the substrate material is
in the form of particles or granules. While particles of any
suitable size may be used, in preferred examples of the invention
the particles or granules have a diameter in the range of 0.05 mm
to 50 mm; a diameter in the range of 0.05 mm to 10 mm, more
preferably a diameter in the range of 0.05 mm to 2 mm.
[0045] Preferably the particulate substrate is such that gas or
vapour can escape from the pressing region in a direction having at
least a component in a direction generally transverse to the
pressing direction in which the sheet-form curable material is
pressed to the substrate.
[0046] The particulate substrate comprises a plurality of
interstitial spaces interstitial spaces such that the material of
the sheet-form curable material passes into the interstitial spaces
of the substrate material during pressing. Herein, references to
`interstitial spaces` means the spaces between the particles or
grains of the material.
[0047] The density of the particulate substrate is such that the
interstitial spaces are large enough to allow flow of gas and/or
air from the pressing region as discussed above.
[0048] The configuration of the substrate is such that it can
release pressure in the pressing region. While substrates with
interstitial spaces of any suitable size may be used, in some
examples, the interstitial spaces are in the range of 0.5 mm to 5
mm in diameter, more preferably 0.5 or 1 mm to 2 or 3 mm in
diameter.
[0049] Any suitable amount of particulate material may be used. In
particular, an amount suitable to allow air and other gasses
produced during pressing and curing to pass through the substrate
interstitial spaces and prevent distortion of the cured polymeric
skin. In a preferred embodiment of the invention an excess of
particulate material is used. In some embodiments the substrate has
a depth of 1 cm to 10 cm, preferably 3 cm to 6 cm.
[0050] In preferred embodiments of the invention the particulate
substrate comprises a material selected from sand, gypsum,
graphite, calcium carbonate, hydrated organic salts, ceramic
materials, ground glass, ground stone, clay materials, metal
oxides, powdered paints, and mixtures thereof. In a preferred
embodiment of the invention the particulate material comprises
sand.
[0051] It will be appreciated that the particulate substrate may
also be used to form a finish to the formed skin. Such finishes
produced may vary according to type and colour, and may be
controlled by the use of the particulate materials used.
[0052] Pigments may be added to the particulate substrate material
in order to control colour. By way of further example, ground glass
can be used to form a desirable texture. Other material for example
grits might be used on their own or in combination to obtain the
desired effect. If stone or a material other than sandstone is to
be simulated or a different effect is being obtained, the
particulate might include other materials or mixtures of materials,
for example carbon containing materials, graphite, clay, marble
and/or coloured dust. The particulate may include a mixture of
different coloured particulates which have been pre-sorted, or
coloured. A colouring treatment may be applied to the particulates
before pressing, and/or could be applied after formation of the
skin.
[0053] Alternatively, or in addition, the material may be coloured
to give an attractive finish.
[0054] Different colours or textures of finish may be used as
required. Where other effects are to be obtained, the particulate
material may include other materials, for example grains having low
or high hardness, angular or smooth shape, be of different sizes
and/or of different natural colours. The particulates are
preferably insoluble, but this might not be essential, for example
where the resulting product is to be used in an internal
application and not exposed to weathering. The particulates may
comprise individual particles, or might comprise a powder, for
example compressed to form granules.
[0055] Different coloured sands may be used to produce an
attractive and realistic stone or brick effect; different coloured
sands may be used to produce an attractive pattern. It will be
understood that surface finishing effects may include, for example,
brick, stone, marble, stucco, and slate.
[0056] In some examples, larger particles can be used. In some
cases, gravel or pebbles can be embedded into the skin using
methods described. Thus a "pebble dashed" effect can be achieved.
For example, exterior skins for houses having a pebble dashed
appearance can be formed.
[0057] The particulate substrate may also comprise one or more
materials susceptible to electromagnetic radiation, for example one
or more materials susceptible to microwave radiation. Suitable
materials may include one or more of graphite, carbon black,
metals, metal oxides, hydrated inorganic salts or compounds,
hydrated organic salts or compounds, water, or ceramic
materials.
[0058] The method of the present invention comprises the step of
providing a sheet-form curable material, and contacting the
particulate substrate with a first surface of the sheet-form
curable material. In such a step, the particulate substrate
preferably covers substantially all of the sheet-form material.
[0059] The sheet-form curable material preferably comprises a
thermoset. The material may include further components, for example
components to enable the material to be handled in sheet-form.
[0060] The sheet-form curable material of aspects of the invention
may include any appropriate matrix composition. For example, the
matrix may include one or more of a thermosetting polymer, for
example an epoxy resin, a phenolic resin, a polyester resin, a
polyvinylester resin, a bismaleimide or polyimide, and/or any other
suitable material. The material may include melamine, which is
useful as a fire retardant. The matrix materials may further
include hardeners, accelerators, fillers, pigments, and/or any
other components as required. The matrix may include a
thermoplastic material.
[0061] The sheet-form curable material may have a thickness of 0.3
to 20 mm, such as 0.5 to 10 mm.
[0062] With regard to the use of phenolic resins, the prior art
(see for example U.S. Pat. Nos. 3,005,798, 3,663,503 and 4,369,259)
teaches that in order to produce a phenolic resin with limited or
reduced colour change, both a colour-stabilising agent and an acid
catalyst must be present. Clearly, the requirement of both
reactants will increase the costs of producing lighter coloured
resins.
[0063] Furthermore, as shown in some of the above mentioned
documents, the colour stabilising agent may be required to be added
at a specific point in the reaction process (i.e. whilst the phenol
resin is still in water-soluble form) in order to achieve the
colour-stabilising effect throughout the resin formed. This creates
a more complex reaction process, which will inevitably affect time
efficiency and therefore, once again, cost efficiency of producing
such resins.
[0064] In addition, many of the methods available for producing
lighter coloured phenolic resins require the presence of strong
acids or bases to catalyse the reaction process. It is known that
the use of such chemicals causes corrosion of equipment which will
therefore need to be replaced more frequently.
[0065] In accordance with the present invention, where a phenolic
resin is used, it is preferable for wherein the thermosetting
material to comprise: [0066] uncured phenolic resin; [0067] filler;
[0068] a catalyst in an amount of less than 2 wt. % relative to the
content of phenolic resin; and wherein the filler is present in a
ratio of filler to uncured phenolic resin in an amount of 2.5:1 and
greater, and further wherein the filler comprises a transition
metal hydroxide and/or aluminium hydroxide in a ratio of metal
hydroxide to uncured phenolic resin in an amount of 1:1.5 to
3:1.
[0069] It has been surprisingly found that the addition of a metal
hydroxide compound within the filler allows for the amount of
catalyst present to be significantly reduced, and even possibly
avoided altogether.
[0070] Without wishing to be bound by any particular theory, it is
believed that the addition of the metal hydroxide compound allows
for the uncured phenolic material to reach an equivalent of B-stage
curing without the need for a catalyst to be present in any
significant quantity, or even at all.
[0071] As would be fully understood by persons of skill in the art,
the B-stage refers to partially cured state which allows for
increased processability of such phenolic resins, for example,
allowing them to be formed into sheets which may then be applied to
a substrate and/or surface. The stability is such that the formed
sheets can be formed into rolls for storage and later use. Such
materials can then be fully cured by the application of heat and
pressure.
[0072] As discussed above in some detail, a problem with the use of
traditional catalysts is the discolouration of the cured resin
produced, and therefore the ability to produce composites of
different colour finishes and patterns. By use of the material
disclosed herein, it is possible to reduce or even alleviate such
issues as the amount of catalyst can be used, and in some
embodiments avoided altogether.
[0073] Preferably, the amount of catalyst that is present may be
less than 1 wt. % relative to the content of the phenolic resin,
more preferably less than 0.5 wt. % relative to the content of the
phenolic resin, such as less than 0.2 wt. %.
[0074] In some embodiments, the uncured material may be
substantially free of catalyst. By substantially free, it is meant
that the amount of any catalyst present is negligible in terms of
the overall effect that it has on uncured material, and its ability
to reach a B-stage equivalent of curing.
[0075] Accordingly, a further aspect of the present invention
provides an uncured material for forming a phenolic resin sheet
consisting essentially of: [0076] uncured phenolic resin; and
[0077] filler; wherein the filler is present in a ratio of filler
to uncured phenolic resin in an amount of 2.5:1 and greater, and
further wherein the filler comprises a transition metal hydroxide
and/or aluminium hydroxide in a ratio of metal hydroxide to uncured
phenolic resin in an amount of 1:1.5 to 3:1.
[0078] It will also be appreciated that the uncured materials
disclosed herein may be free of catalyst.
[0079] For the avoidance of any doubt, the term catalyst is
intended to refer to additives which are known to catalyse the
curing of such phenolic resins, and are known to aid B-stage
curing. Traditionally, such catalysts fall into two main
categories, namely acidic and basic. Examples of acidic catalysts
include, but are not limited to, one or more of hydrochloric acid,
sulphuric acid and oxalic acid. Examples of basic catalysts
include, but are not limited to, one or more of ammonia, sodium
hydroxide, potassium hydroxide, lithium hydroxide, rubidium
hydroxide, caesium hydroxide, barium hydroxide, calcium hydroxide
and ethylamine.
[0080] It will also be appreciated that by reducing the presence of
the catalyst material, or even avoided its presence altogether, it
is possible to avoid discolouration issues without the need to add
colour-stabilising agents, for example, glyoxal, thiones,
phosphinic acid salts, phosphonic acid salts such as described
above.
[0081] Accordingly, yet a further aspect of the present invention
provides an uncured material for forming a phenolic resin sheet
consisting of: [0082] uncured phenolic resin; [0083] filler; [0084]
optionally, further additives specifically as described herein; and
wherein the filler is present in a ratio of filler to uncured
phenolic resin in an amount of 2.5:1 and greater, and further
wherein the filler comprises a transition metal hydroxide and/or
aluminium hydroxide in a ratio of metal hydroxide to uncured
phenolic resin in an amount of 1:1.5 to 3:1.
[0085] In accordance with the uncured materials described herein
(including sheet-form materials in general), the filler may be
present in an amount of 3:1 and greater, and preferably in an
amount of 3.5:1 and greater. It will be appreciated that the amount
of filler which is added is dependent, in some instances on the
intended use of the composite being prepared. It will also be
appreciated that there is a significant economic advantage in being
able to increase the amount of filler whilst still being able to
meet the stringent requirements for such composites, such as
strength, modulus, fire resistance, weathering resistance etc.
Accordingly, the amount of filler present may also be in an amount
of 5:1 and greater where applicable.
[0086] Suitable fillers for use in the sheet-form curable materials
include particulate solids which are insoluble in the thermosetting
material, such as filler selected from one or more of clays, clay
minerals, talc, vermiculite, metal oxides, refractories, solid or
hollow glass microspheres, fly ash, coal dust, wood flour, grain
flour, nut shell flour, silica, ground plastics and resins in the
form of powder, powdered reclaimed waste plastics, powdered resins,
pigments, and starches.
[0087] In accordance with the uncured materials described herein
(which includes in general the sheet-form materials described
herein), the amount of filler may be present in an amount of 20:1
and less, such as in an amount of 10:1 and less.
[0088] The uncured phenolic compositions described herein are
particularly concerned with phenol-formaldehyde resins.
[0089] In general, the fillers used in the sheet-moulding materials
described herein may be any particulate solid which insoluble in
the resin mixture.
[0090] As will be appreciated, it is preferable that the filler is
inert to the rest of the uncured material.
[0091] The fillers used may be organic or inorganic materials. For
some embodiments, it is preferable for the filler to be an
inorganic material.
[0092] Suitable fillers for use in the uncured phenolic materials
described herein may be selected from one or more of clays, clay
minerals, talc, vermiculite, metal oxides, refractories, solid or
hollow glass microspheres, fly ash, coal dust, wood flour, grain
flour, nut shell flour, silica, ground plastics and resins in the
form of powder, powdered reclaimed waste plastics, powdered resins,
pigments, and starches.
[0093] As discussed above, it has been surprisingly found that the
addition of a transition metal and/or aluminium hydroxide compound
has the surprising effect of allowing the amount of catalyst to be
greatly reduced and possibly avoided altogether with respect to
phenolic resin systems.
[0094] Preferably, the transition metal or aluminium hydroxides are
selected from compounds of formula M(OH).sub.3, wherein M is a
metal.
[0095] Suitable metals (M) may be selected from one or more of
scandium, vanadium, chromium, manganese, iron, cobalt and
aluminium. In a preferred embodiment, the metal hydroxide is
aluminium hydroxide.
[0096] In the materials described herein, the transition metal
and/or aluminium hydroxide may be present in a ratio of metal
hydroxide to uncured phenolic resin in an amount of 1:1.6 to 2.5:1,
such as a ratio of metal hydroxide to uncured phenolic resin in an
amount of 1:2 to 2:1.
[0097] In addition to the transition metal and/or aluminium
hydroxide in the compositions described herein, the uncured
phenolic material may further comprise ethylenediaminetetraacetic
acid (EDTA). However, it is not in any way essential to the present
inventions.
[0098] In preferred embodiments of the materials described herein,
the fillers do not substantially comprise silicates and/or
carbonates of alkali metals. This is due to the fact that solids
having more than a slightly alkaline reaction, for example
silicates and carbonates of alkali metals, are preferably avoided
because of their tendency to react with acid hardeners. However,
solids such as talc, which have a very mild alkaline reaction, in
some cases because of contamination with more strongly alkaline
materials such as magnesite, are acceptable for use as fillers.
[0099] As discussed above, the use of the transition metal and/or
aluminium hydroxide compound allows for the amount of catalyst used
to be reduced, or even avoided altogether. A significant benefit of
this is that issues known in the art associated with discolouration
can be avoided, thus allowing for the use of pigments which
previously would not have been suitable, especially for commercial
uses where finishes are of great importance.
[0100] It will also be understood that suitable colours may include
white, yellow, pink, red, orange, green, blue, grey or purple. The
reduction in catalyst and therefore the associated discolouration
means that lighter colours may now be produced, for example, white,
yellow, pink, red, orange, as well as light green, blue, grey and
purple. The ability to produce finishes having such light colours
greatly improves the commercial applications of such materials.
[0101] Phenolic resin materials such as described herein have
significant advantages over more traditional materials such as SMC.
It has been found that the phenolic resin material disclosed herein
generally has the following advantages over SMC: [0102] Better
temperature performance and thermal shock resilience [0103] The
phenolic materials of the present invention can be used to form
brake pads, foundry moulds, aerospace heat shields etc. [0104]
Excellent resistance to chemicals, corrosives/solvents, oil and
water/salt water (including acid rain) [0105] The phenolic
materials of the present invention can be used to make laboratory
countertops [0106] Improved fire, smoke and toxicity performance
[0107] The phenolic materials of the present invention can be used
in mass transport and defence applications [0108] Improved
anti-microbial properties [0109] Harder, stronger, excellent
dimensional stability [0110] Electrical resistance [0111] Good
thermal insulation [0112] Superior workability [0113] Low
temperature processing
[0114] The uncured materials described herein may further comprise
a viscosity controlling agent.
[0115] Suitable viscosity controlling agents may be selected from
one or more of butanol, chloroform, ethanol, water, acetonitrile,
hexane, and isopropyl alcohol. In a preferred embodiment, the
viscosity controlling agent is water.
[0116] It will be appreciated that the amount of viscosity
controlling agent used is dependent on the intended use of the
uncured material. It is considered that the controlling of the
viscosity is within the knowledge of the person of skill in the
art.
[0117] The sheet-form curable material may comprise reinforcement,
for example reinforcing fibres. The sheet-form curable material may
include carbon fibres, glass fibres or aramid fibres.
[0118] The fibres may be short fibres, or may be longer fibres. The
fibres may be loose, for example, the fibres may be arranged in a
uni- or multi-directional manner. The fibres may be part of a
network, for example woven or knitted together in any appropriate
manner. The arrangement of the fibres may be random or regular.
[0119] Fibres may provide a continuous filament winding. More than
one layer of fibres may be provided. The fibres may be in the form
of a layer. Where the fibres are in the form of a layer, they may
be in the form a fabric, mat, felt or woven or other
arrangement.
[0120] In an embodiment, the fibres may be selected from one or
more of mineral fibres (such as finely chopped glass fibre and
finely divided asbestos), chopped fibres, finely chopped natural or
synthetic fibres, and ground plastics and resins in the form of
fibres.
[0121] In addition, the fibres may be selected from one or more of
carbon fibres, glass fibres, aramid fibres and/or polyethylene
fibres, such as ultra-high molecular weight polyethylene
(UHMWPE).
[0122] The sheet-form curable material may include short fibres.
The fibres may of a length of 5 cm or less.
[0123] Where present, the fibres may be added to the uncured
material in a ratio of resin to fibre of 6:1 to 1:3, such as a
ratio of from 4:1 to 1:1.
[0124] The sheet-form curable materials may be produced by mixing
of the components as described above so as to form a generally
homogeneous distribution of the components throughout the material.
Any known method may be used to produce the general homogeneous
distribution, such as high-shear mixing.
[0125] The length of time required to produce a generally
homogeneous distribution of the components is dependent on, amongst
other things, the amount of each component added, the viscosity of
the components and the method of mixing used. In general, a
substantially homogeneous distribution of the components can be
formed within 5 minutes to 2 days, preferably within 10 minutes to
1 day, more preferably within 15 minutes to 10 hours.
[0126] The sheet-form curable materials may have a thickness of
from 0.3 to (for example 1 mm to 50 mm) to 50 mm, such as from 2 mm
to 30 mm, or even 3 mm to 20 mm. Sheets of thickness 4 mm to 15 mm
and 5 to 10 mm are also envisaged, as are sheets of 6 mm to 8
mm.
[0127] In an embodiment, the sheet-form curable material comprises
SMC (sheet moulding compound). The SMC comprises a thermosetting
resin, preferably a polyester resin, together with reinforcing
fibres, preferably glass fibres. There are benefits in using SMC.
For example, SMC has low density and favourable mechanical
properties compared with other materials (for example
thermoplastics), and also exhibits good thermal properties. Of
particular importance for some applications, for example building
applications, resistance to fire is good. SMC also shows good noise
reduction qualities, also important where used as a building
material and good chemical resistance.
[0128] The SMC may comprise two main components: a matrix and
fibres. The SMC matrix preferably comprises a resin which
preferably includes polyester, but may include vinyl ester, epoxy,
phenolic, or a polyimide. Preferably the matrix comprises a
thermosetting resin. The SMC matrix may further comprise additives,
for example minerals, inert fillers, pigments, stabilizers,
inhibitors, release agents, catalysts, thickeners, hydrating
additives and/or other suitable materials. Suitable fibres are
discussed above.
[0129] Alternatively or in addition to the presence of fibres in
the sheet-form curable material, reinforcement may be provided as a
separate layer of fibres such as described above, for example
arranged between the sheet-form curable material and the
substrate.
[0130] Where the separate layer of reinforcement is provided, it
may be located across the whole of the substrate, or may for
example be provided in only parts. For example, if there is a
particular section of the product which is more susceptible to
damage or attack, additional reinforcement can be provided in that
region. For example, where the product is to be used in a door,
additional reinforcement may be provided at regions of the door
which are thinner than others for due to decorative moulding or
other features and/or at regions of the door which are more
susceptible to damage. Thus, reinforcement may be provided as one
or more layers separate from the sheet-form curable material. The
additional layer of reinforcement may include short and/or long
fibres, for example of materials mentioned above.
[0131] The method of the present invention may further comprise the
step of providing one or more masonry tiles, the masonry tiles
preferably being applied to the sheet-form curable material prior
to contacting with the particulate substrate.
[0132] The use of such masonry tiles allows for the production of
products having a brick, concrete, stone, tile or glass surface.
Preferred aspects of the invention relate to products comprising a
cured skin and a masonry surface, such as a brick, concrete, stone,
tile or glass surface.
[0133] Structures formed from masonry are traditionally constructed
from masonry blocks which are generally laid in and bound together
by mortar, in some cases with steel reinforcement. Such structures
are generally highly durable, resistant to weathering, have good
weight-bearing properties, and are also visually appealing, making
masonry a widely-used construction material. However, masonry does
have the disadvantages that masonry blocks are heavy,
time-consuming to install, and can be extremely costly.
Particularly in the case of stone blocks, such as granite or
marble, only a small portion of the costly stone is visible in use,
making the use of entire blocks of such stone types unnecessary and
economically prohibitive. Furthermore, traditional masonry
construction techniques do not have the architectural flexibility
that is found with more modern construction techniques, such as
steel or concrete frame buildings. For instance, masonry
construction techniques are generally unsuited to the construction
of very tall buildings due to the weight of the masonry blocks.
More recently, there are also difficulties in obtaining suitable
supplies of masonry products, even allowing for increased
expense.
[0134] There have been various efforts in the art to develop
construction techniques which overcome the disadvantages of
traditional masonry techniques, whilst maintaining the visual
appeal and durability of traditional masonry in the completed
structures. Generally, these techniques involve some kind of
masonry cladding or siding. The terms "cladding" and "siding" are
used herein to refer to the application of a non-structural layer
of masonry to a pre-existing structure, such as a wall or building,
usually to imitate the appearance of a traditional masonry
structure. The masonry layer is generally substantially thinner
than traditional masonry building blocks, being required only for
visual and non-structural purposes. Thus, siding materials often
take the form of a tile or slip having the surface dimensions of a
brick or stone block on the visible surface, but which are
typically only 10 to 30 mm in depth.
[0135] Siding materials may be applied to structures by being
embedded in a layer of mortar coating the surface of the structure,
sometimes with the use of metallic or plastic guide rails, which
are used to maintain even spacing of the siding materials, for
example brick slips. Another technique involves the use of metallic
ties or clips which tie the siding materials to the underlying
structure and which also transfer the weight of the siding
materials to the building structure. Often metallic ties or clips
and mortar are used in combination. Usually a pointing substance is
subsequently disposed in the spaces between the siding materials to
complete the illusion of a traditional masonry structure.
[0136] The use of siding materials, whilst having some advantages
over traditional masonry construction techniques, nonetheless has
the disadvantage that the installation of large numbers of separate
siding tiles remains comparatively times consuming, particularly
where the materials still require pointing.
[0137] The present invention provides the particular advantage of
being to produce siding materials where the masonry tile and
grouting can be formed in situ, and at the same time during the
pressing step. Such a process significantly reduces the duration
for formation of siding panels, and indeed the duration of
construction projects.
[0138] As used herein, the term "masonry tile" is intended to refer
to a tile formed, at least in part, from concrete, clay, natural
stone, artificial stone, ceramic, glass, or a combination
thereof.
[0139] For example, the masonry tile may be formed from brick,
marble, granite, limestone, travertine, sandstone, slate, cast
stone, porcelain, earthenware, glass, or other similar materials,
or a combination thereof. For the avoidance of doubt, as used
herein, the term masonry tile should not be interpreted to include
wood.
[0140] Where the masonry tile is formed from a porous material such
as clay, porcelain or earthenware, it may be at least partially
glazed. For example, the visible surface may be glazed, with the
surface that contacts the sheet-form material remaining unglazed.
As will be appreciated by persons of skill in the art, an unglazed
surface provides a better surface for attachment to the sheet-form
material and is therefore preferable to form a strong bond.
[0141] The depth of the masonry tile is preferably less than 30 mm,
more preferably less than 20 mm, and still more preferably less
than 15 mm. Generally, a depth of at least 5 mm is preferred for
reasons of durability, although with smaller masonry tiles the
depth may be less than 5 mm, for example from 2 to 5 mm, e.g. 3 mm
or 4 mm.
[0142] Suitably, the masonry tile has a depth in the range of from
3 to 30 mm, more preferably 3 to 15 mm, for example 5 to 15 mm, or
5 to 10 mm.
[0143] Generally, the surface area of the masonry tile will not be
greater than about 500 mm by 500 mm. However, the exact size of the
masonry tile depends on the type of material used to form the
masonry tile and the desired visual effect of the composite
product. For instance, where the composite product is intended to
look like a brick wall, the masonry tiles advantageously have a
surface area of from about 190 to about 250 mm by about 55 to about
75 mm to simulate the dimensions of a major side face of a standard
building brick.
[0144] Alternatively, the masonry tile may have a surface area of
from about 95 to about 125 mm by about 55 to about 75 mm to
simulate the dimensions of an end face of a standard building
brick. For example, the masonry tile could be cut from a standard
building block, such as a standard building brick. Alternatively,
the masonry tile could be a brick slip of the type known in the
art.
[0145] In the United Kingdom a standard size building brick
generally has a major side face of about 65 mm by about 215 mm and
an end face of about 65 mm by about 102. 5 mm. In the United States
a standard size building brick generally has a major side face of
about 57 mm by about 203 mm and an end face of about 57 mm by about
102. 5 mm.
[0146] Where the composite product is intended to look like a stone
wall, a larger masonry tile size may be appropriate.
[0147] The surface of the masonry tile that contacts the sheet-form
material may be provided with surface indentations, pores or
protrusions to form a key to ensure a strong bond is formed between
the sheet-form material and the masonry tile. For example, a series
of parallel or crossed grooves may be provided. In some cases,
however, the masonry material may have a sufficiently coarse
structure that the provision of surface indentations or protrusions
is unnecessary for a strong bond to be formed between the
sheet-form material and the masonry tile.
[0148] The masonry tile may extend over substantially all or only a
part of the sheet-form material and/or the substrate area.
Preferably, a plurality of masonry tiles is provided which
collectively extend over substantially all or only a part of the
sheet-form material and/or the substrate area. In this way, the
plurality of masonry tiles may be rigidly bonded onto the surface
of the sheet-form material and the substrate in any desired
arrangement. For example, the plurality of masonry tiles may
desirably arranged so as to imitate the arrangement of masonry
building blocks found in traditional masonry construction
techniques, for example the traditional brickwork bonds (e.g.
Flemish bond, stretcher bond, English bond, header bond,
herringbone bond and basket bond).
[0149] Optionally, the plurality of masonry tiles may be spaced
apart and a rendering or grouting provided by the particulate
substrate in the spaces between the masonry tiles to simulate the
appearance of bricks bonded together by mortar, or a tiled wall or
floor.
[0150] Alternatively, a particulate material, such as sand,
powdered brick, powdered stone or powdered ceramic, may be pressed
into the sheet form material in the spaces between the masonry
tiles to simulate the appearance of render or grout. Preferably,
the particulate material is pressed into the sheet form material
simultaneously with pressing of the masonry tile, the sheet form
material and the particulate substrate to form the skin.
[0151] In some embodiments, the method of the present invention may
further include a step of contacting a surface material in
particulate form with a second surface of the sheet-form curable
material.
[0152] The method of the present invention may further include the
step of applying the sheet-form curable material to a mould.
[0153] Such moulds are well known in the art and may be used to
shape the final skin. By way of example, the mould may be
contoured.
[0154] In a preferred embodiment, the mould may be in the form of a
template, such as a template defining a pattern to be formed by the
masonry tiles. Such a template may be used to help position the
masonry tiles when forming a skin.
[0155] The template may also be used to control the profile of the
sheet-form material between the masonry tiles. For the avoidance of
doubt, the template can be used to control the depth of the skin in
the area between the masonry tiles. Such control allows the
position of the grout or render between the masonry tiles to be
controlled.
[0156] In certain countries, it is known for the grout or render to
be lower than the upper surface of the masonry (i.e. the grout or
render is sunken compared to the masonry). In other countries, it
is preferred for the grout or render to be at a height similar to
that of the upper surface of the masonry.
[0157] It will also be appreciated that the use of a mould template
enables the present invention to be used to produce a range of
different styles in situ without needing complicated mould systems
or multiple processes.
[0158] The mould template, in use, also results in a set of
channels in the back surface of the cured skin. Such channels may
be particularly beneficial with resect to allowing the flow of air
behind the skin once installed.
[0159] In a preferred embodiment of the invention, the method
comprises: [0160] optionally providing a template on a press;
[0161] providing a sheet-form curable material on the press [0162]
arranging masonry tiles on a surface of the sheet-form curable
material to form a pattern; [0163] applying a particulate substrate
such that it covers at least any remaining surface area of the
sheet-form material to the height of the masonry tiles (and
preferably also the masonry tiles); [0164] pressing the sheet-form
curable material to the substrate, and [0165] at least partially
curing the sheet-form curable material, wherein the configuration
of the particulate substrate is such that gas and/or vapour can be
displaced from the pressing region, and a portion of the sheet-form
curable material flows into the particulate substrate.
[0166] Preferably the viscosity of the sheet-form curable material
is reduced during the pressing step. Preferably the sheet-form
curable material is one that reduces in viscosity and/or at least
partially liquefies on the application of heat and/or pressure.
Preferably, during the pressing step, at least a portion of the
sheet-form curable material flows into the interstitial spaces of
the particulate substrate. the sheet-form curable material and
particulate substrate are such that only a portion of the
sheet-form curable material flows into the substrate during the
moulding step so that a suitable skin thickness for the required
mechanical and other properties of the skin are retained on the
surface of the particulate substrate.
[0167] Preferably the sheet-form curable material is applied to the
substrate in uniform thickness.
[0168] The sheet-form curable material is applied to the substrate
in unfolded form. A plurality of single thickness layers may be
provided, the layers preferably overlapping at the edges to reduce
the risk of gaps being formed in the skin.
[0169] Preferably the sheet-form curable material is applied to
substantially a whole mould surface.
[0170] The present invention includes a step of pressing the
sheet-form curable material to the substrate. Preferably the
pressure applied is less than 200 tonnes per m.sup.2, preferably
less than about 100 tonnes per m.sup.2. In many examples, the
pressure applied will be equivalent to less than about 50, 25, 10
or even less than about 5 kg/cm.sup.2.
[0171] As discussed above, traditional SMC manufacturing processes
requires enormous pressure to evacuate the air trapped during the
forming of the SMC product and that solid porous substrates were
previously known to at least partially alleviate trapped air.
Surprisingly, the present invention has found that by putting a
particulate substrate behind the SMC skin prior to pressing, the
air can escape though the interstitial spaces of the particulate
structure reducing potential deformation of the cured skin
material.
[0172] With respect to the use of phenolic resins, the particulate
substrate functions similarly and allows vapours produced during
curing to be removed from the pressing region.
[0173] In an embodiment of the invention the sheet-form curable
material is applied to a mould surface. The mould may comprise
aluminium or an aluminium alloy. Where lower pressures are used,
aluminium tools can be used. This can give rise to low cost
tooling, flexible production and less downtime due to tool change
over in view of the reduced weight of an aluminium mould and speed
of heating or cooling an aluminium mould compared with a stainless
steel mould. For example, the volume of an aluminium tool could be
significantly smaller than that of a corresponding tool of steel,
and this combined with the lower density of aluminium leads to
considerable weight advantages when using aluminium moulds. Where
reference is made herein to components being made of or comprising
aluminium, preferably the relevant component includes aluminium or
an appropriate aluminium alloy or other material including
aluminium.
[0174] The method may include a step of providing further
components, such as between the mould and the sheet-form curable
material.
[0175] The method further includes the step of providing a veil on
a second surface of the sheet-form curable material. In one
embodiment the veil is provided between the sheet-form curable
material and a surface of the mould. Preferably the veil comprises
a sheet of material which is provided between the sheet-form
curable material and the mould surface before pressing. The
provision of the veil preferably gives rise to improvements or
changes in the surface finish of the moulded article compared with
an arrangement in which the veil is not present.
[0176] The veil is preferably substantially pervious to a component
of the sheet-form curable material during pressing. In this way, a
component, for example a resin component, of the sheet-form curable
material can pass through the veil during moulding so that a resin
finish at the surface of the cured product can be formed.
Therefore, the material for the veil is preferably chosen so that
it is sufficiently pervious to certain components of the sheet-form
curable material (in particular the resin), while providing a
barrier function for certain other components for example glass
fibres or other reinforcements.
[0177] In some arrangements the veil can be placed directly
adjacent to the mould surface and there will be sufficient
penetration by resin components for a satisfactory surface finish
to be produced.
[0178] The veil may comprise a non-woven material. In particular
where the veil is applied directly to the mould, it may be desired
for the veil material not to have a particular texture or finish,
which might form a perceptible surface structure at the surface of
the moulded product. However, in other arrangements, such a surface
structure or pattern at the surface may be an advantageous
feature.
[0179] Where such a structure is not desired, preferably the veil
comprises a non-woven material. For example, preferably the veil
does not comprise a knitted or woven surface, although in some
cases such a material could be used, in particular if a surface
treatment had been provided to reduce the surface structure of the
veil material. For example, in some arrangements, the veil might
comprise a fleece or brushed surface. In some arrangements, the
veil may comprise a surface pattern which can be seen through the
cured skin product. However, for most applications, preferably at
least one surface of the veil material has substantially no surface
structure or pattern.
[0180] The veil may comprise a felt cloth. For example the veil may
comprise a polyester material. Alternative materials could be used,
for example comprising wool, polyethylene, polypropylene or PET.
The veil might comprise a fleece material, or might comprise a foam
material. As indicated above, a suitable material preferably is
pervious to the resin to be used, and has a suitable surface
texture. The veil may comprise a polyester material, having a
weight of about 120 to about 150 g/m.sup.2.
[0181] In some embodiments the method comprises spreading
particulate substrate material across the mould surface, applying
the sheet-form curable material to the mould, the sheet-form
curable material covering the grains, and pressing the sheet-form
curable material to the mould to form the skin having the
particulates bonded and/or embedded in its surface.
[0182] In other embodiments the sheet-form material is applied to
the mould before the particulate substrate material.
[0183] It will be appreciated that, in principle, particulate
substrate material may be applied on both first and second surfaces
of the sheet-form curable material, so that a surface effect is
produced on both surfaces.
[0184] The process of the present invention allows different
surface finishes to be present on a single cured skin. By way of
example, one surface of the skin may have a smooth finish, and the
other surface a stone effect finish.
[0185] Likewise, the surface finishes on both sides may be
identical.
[0186] It will also be appreciated that it is unnecessary for the
particulate material of the substrate to be the desired surface
finish for the cured skin. It may well be that the desired finish
is the opposite surface of the cured skin. Such a surface may be
nothing more than the cured sheet-form curable material, which for
example could be glossy or matt in finish, and potentially
coloured. Such skins could be used, for example, to form body
panels for vehicles, or panels for buildings (both interior and
exterior).
[0187] The particulate substrate material generally becomes
embedded in a matrix of the sheet-form curable material. Depending
on the materials used and the manner of pressing the components
together, the grains may extend from the surface of the matrix
material, or may be embedded or submerged in the surface.
[0188] The methods of the present invention may further comprise
the step of carrying out a surface treatment to increase exposure
of the grains in the surface. The surface treatment may include
removing surface material or matrix from around the grains.
[0189] The method may further include the step of sandblasting the
surface containing the grains of surface material. The term
sandblasting should preferably be understood to include any
technique in which particles are propelled onto the surface to
remove part of the matrix material and thus to expose the grains in
the surface. Any appropriate method may be used. The sand blasting
may be carried out for example by air blasting sand particles at
the surface.
[0190] Thus in examples the surface formed has a polymer matrix,
but also includes particulate substrate material which gives a
realistic look to a simulated surface.
[0191] The present invention includes a step of pressing the
sheet-form curable material to the particulate substrate. In
embodiments where the method of the present invention includes one
or more of a mould, masonry tiles, a veil or further particulate
material, these components are also pressed to the sheet-form
curable material. Preferably the pressing is carried out in a
single step to form the product. In some examples, the pressing
step can form the final product without further machining or other
finishing steps being required.
[0192] The method of the present invention also includes a step of
at least partially curing. The step may include heating the
sheet-form curable material. When heated the sheet-form curable
material cures to form the skin. In some embodiments the curing
step comprises heating the sheet-form curable material to a
temperature greater than 100.degree. C., preferably to a
temperature greater than 120.degree. C. Heating may improve the
flow of the sheet-form curable material.
[0193] In some embodiments of the invention, pressing and heating
occur simultaneously. In embodiments where the substrate is applied
to a press, i.e. a press plate, the press may be a heated press.
Alternatively, in embodiments where the sheet-form curable material
is applied to a mould, the method may include a step of heating the
mould whereby the sheet-form curable material is heated by the
heated mould.
[0194] In other embodiments of the invention the particulate
substrate is heated prior to contact with the sheet form curable
material. In these embodiments, the method includes a step of
heating the particulate substrate. The particulate substrate may be
heated to a temperature described above and then contacted with the
sheet-form curable material whereby the sheet-form curable material
is heated. In one embodiment the substrate is heated via induction
heating. In a separate embodiment the substrate is heated by
irradiation with an electromagnetic radiation.
[0195] Preferably the electromagnetic radiation comprises radiation
with a frequency of from 300 MHz to 300 GHz, preferably from 300
MHz to 30 GHz, more preferably from 300 MHz to 3 GHz. In a
preferred embodiment of the present invention, the electromagnetic
radiation comprises radiation with a frequency of from 800 MHz to
1000 MHz, preferably from 902 MHz to 928 MHz. In an alternative
preferred embodiment of the present invention, the electromagnetic
radiation comprises radiation with a frequency of from 2.2 GHz to
2.7 GHz, preferably from 2.4 GHz to 2.5 GHz.
[0196] Preferably the particulate substrate is irradiated with
electromagnetic radiation with a power of at least 500 W, more
preferably at least 700 W, for example at least 800 W. Any suitable
power may be used for the irradiation and it will be understood
that industrial irradiation systems with much higher power output
may be used depending on the specific application. For example the
power of the irradiation system may be at least 100 kW or at least
1 MW.
[0197] The irradiation may be conducted by any method known in the
art. In some embodiments, where the electromagnetic radiation
includes microwave radiation, the irradiation is conducted by means
of a microwave oven, although other methods of emitting
electromagnetic radiation may also be used.
[0198] According to a preferred embodiment the irradiation of the
particulate substrate is conducted for a time period of from 30
seconds to 6 minutes. Irradiation of the substrate with
electromagnetic radiation allows the particulate substrate to be
heated rapidly throughout its structure. Therefore, the step of
curing the sheet-form curable material may be conducted more
rapidly than with the traditional heated press, increasing
productivity and minimising damage to sensitive components.
[0199] The particulate substrate may be heated to any suitable
temperature such that the curing of the sheet-form material is
commenced. Preferably, the substrate is heated to a temperature of
from 100.degree. C. to 250.degree. C., preferably from 120.degree.
C. to 200.degree. C.
[0200] After irradiation and resultant heating of the particulate
substrate to a temperature such that the curing of the sheet-form
curable material is commenced, the particulate substrate may cool
slowly to the extent that the curing of the sheet-form material
continues after the period of time in which the particulate
substrate is irradiated. Therefore, in a preferred embodiment, the
sheet-form curable material is allowed to cure for at least 3
minutes after the irradiation of the particulate substrate is
completed.
[0201] Providing heating by irradiation of the particulate
substrate and not of the sheet-form curable material is
advantageous for at least the following reasons. Firstly, as the
sheet-form curable material forms a skin with an exposed surface,
including magnetic susceptor materials in the sheet-form curable
material will change the appearance of the sheet-form material and
produce an inferior product. Secondly, volatile compounds will be
produced in both the manufacture of the substrate and from the
curing of the sheet-form curable material. Such volatile compounds
are undesirable in the final product as they may have associated
health risks and such compounds are also likely to be flammable.
Heating the particulate substrate has the advantage of removing
such impurities from the substrate, wherein the volatile compounds
may be vaporised and pass out of the substrate through its
interstitial spaces, rather than collecting in the interstitial
spaces.
[0202] According to a preferred embodiment, the particulate
substrate comprises one or more electromagnetic susceptor
materials. In some embodiments, the particulate substrate comprises
more than one electromagnetic susceptor materials. For the purposes
of the present invention, an electromagnetic susceptor material is
considered to be a material which is increased in temperature upon
irradiation with electromagnetic radiation. In a preferred
embodiment, the electromagnetic susceptor material is a microwave
susceptor material, wherein the term microwave is considered to
include electromagnetic radiation with a frequency of from 300 MHz
to 300 GHz.
[0203] The one or more electromagnetic susceptor materials will
preferably be added as a filler to the particulate substrate.
[0204] Electromagnetic or microwave susceptor materials may
comprise any such materials commonly known in the art. Preferably,
the electromagnetic or microwave susceptor material comprises one
or more of graphite, carbon black, metals, metal oxides, hydrated
inorganic salts or compounds, hydrated organic salts or compounds,
water, or ceramic materials. The hydrated inorganic salts or
compounds may comprise one or more of hydrated sulfates, hydrated
phosphates, hydrated zeolites, or hydrated silicates. The hydrated
inorganic salt or compound preferably comprises gypsum or clay
minerals. In a particularly preferred embodiment, the
electromagnetic or microwave susceptor material comprises graphite
or gypsum.
[0205] In some embodiments, the properties of the substrate may be
tailored by adjusting the ratio of the different electromagnetic
susceptor materials present in the particulate substrate or the
overall amount of electromagnetic susceptor materials in the
substrate. For example the precise rate and magnitude of the
heating of the particulate substrate may be adjusted in this
way.
[0206] In some embodiments, a pressing or moulding step is
conducted prior to irradiation the substrate. In other embodiments,
a pressing or moulding step is conducted at the same time as the
irradiation of the substrate and the curing of the sheet-form
material.
[0207] In an embodiment of the invention the method comprises the
steps of providing a substrate in particulate form on a press;
providing a sheet-form curable material; contacting the sheet-form
curable material with an upper surface of the substrate; pressing
the sheet-form curable material to the substrate, and curing the
sheet-form curable material, wherein the configuration of the
substrate is such that gas and/or vapour can be displaced from the
pressing region, and a portion of the sheet-form curable material
flows into the first surface of the substrate, this providing a
surface effect to the skin.
[0208] In this embodiment the sheet-form curable material is placed
on a top surface of the substrate, that is, above the substrate.
This may enable the sheet-form curable material to flow more easily
into the substrate interstitial spaces.
[0209] An advantage of the methods described herein is that the
cured polymeric skins of the present invention may have a surface
effect which arises from the particulate substrate. During the
pressing step, some of the particulate substrate material becomes
embedded in a matrix of the sheet-form curable material. Depending
on the substrate materials used and the manner of pressing the
components together, the substrate particles may extend from the
surface of the matrix material, or may be substantially embedded or
submerged in the surface. After the curing step, the particulate
substrate material may be brushed off the cured polymeric skin
material with the exception of the particles which have been
embedded in the matrix. These embedded particles may remain and
form a surface effect on the skin.
[0210] Surprisingly, it has been found that any particulate
material which has not bonded to the skin may be brushed from the
skin after curing leaving a cured polymeric skin with a surface
effect. This is advantageous over known methods which provided open
celled substrates. In these methods the sheet-form curable material
bonded to the open celled substrate during the curing step and
therefore had to be machined off in order to separate the skin from
the substrate.
[0211] In some embodiments of the invention, and as described
above, a surface effect material may also be used, as well as the
particulate substrate. In these embodiments a skin may be formed
wherein a first particulate material is present on a first surface
of the skin; and a second particulate material is present on a
second surface of the skin.
[0212] In a further aspect, the present invention includes a cured
polymeric skin formed by a method as described herein.
[0213] Such cured polymeric skins may comprise at least a portion
of the particulate substrate material is present on a surface of
the skin; and optionally a particulate material is present on a
second surface of the skin.
[0214] The cured polymeric skins may comprise one or more masonry
tiles present on a surface of the skin as well as at least a
portion of the particulate substrate material. Preferably, the
masonry tiles are in a pattern, and the particulate substrate
material is between the masonry tiles forming the pattern.
[0215] In a preferred embodiment, the cured polymeric skin
comprises masonry tiles which are brick-slips in the pattern of a
traditional brick wall, and the particulate substrate material
forms a grout for the bricks.
[0216] In such cured polymeric skins, the sheet-form material is
preferably bonded to the masonry tile and/or the particulate
substrate material. The presence of the particulate substrate
material may also help with bonding of the masonry tiles.
[0217] In another aspect the present invention provides the use of
a particulate substrate in a method such as described herein
above.
[0218] The following non-limiting Examples illustrate the present
invention.
Example 1
[0219] The following examples illustrate production of a cured skin
using a sand substrate.
[0220] A wooden frame was provided on a flat surface and a
substrate comprising sand as the particulate substrate material was
provided inside the frame. The sand used had a particle diameter of
between 0.6 mm and 2.0 mm and the substrate was around 5 cm
deep.
[0221] On top of the sand was provided a sheet of SMC material, the
SMC sheet extended across the whole of the top surface of the
substrate. Downward pressure of around 100 tonnes per m.sup.2 was
then applied to the components. The SMC material was pressed to the
substrate and heated to around 140.degree. C. On heating the SMC
material began to liquefy and flow into the interstitial spaces of
the substrate.
[0222] Air and other gasses trapped between the substrate and the
SMC passed through the porous structure of the sand substrate. The
components were held in the mould with an application of pressure
for a sufficient time for the SMC to cure.
[0223] Once cured, the SMC skin material was removed from the sand
and any excess sand on the substrate was brushed off to leave a
cured SMC skin with a surface effect in the surface which was in
contact with the substrate.
Example 2
[0224] The following example will be described with reference to
FIG. 1.
[0225] A wooden frame (13) was located at an assembly station and
the sand substrate (14) was placed inside the wooden frame.
Immediately on top of the sand substrate was placed a sheet of SMC
(12), the size of the sheet of SMC was so that it was similar to
that of the frame surface. Immediately onto the SMC surface was
placed a printed veil (11). The veil was sized so as to fit to the
SMC surface with little overlap, (the veil may be oversized, in
which case trimming may be required after moulding). A press (10)
was then placed immediately on top of the veil surface.
[0226] The wooden frame and substrate base were then placed onto a
lower heated press platen in a press. In this example, the
temperature of the lower platen was chosen so that the mould
temperature during moulding was about 140.degree. C. An upper
platen was then lowered towards the lower platen in the press and
pressure applied to effect the moulding operation and form a
moulded product. The skin was then removed from the stack of
materials and the excess sand brushed off the bottom of the skin to
form a skin with two surface effects.
Example 3
[0227] The following example will be described with reference to
FIG. 2.
[0228] A mould (24) was heated to 140.degree. C.
[0229] A wooden block (not shown) was placed on the mould and was
filled with a sand substrate (22).
[0230] A sheet of SMC material (20) was then applied to the whole
area of the sand substrate.
[0231] Downward pressure of around 100 tonnes per m.sup.2 was
applied to the components.
[0232] After cooling, the resulting product was removed from the
mould. The sand from the particulate substrate was present on one
side of the SMC, where it was pressed to the sand substrate (22),
with any excess being brushed off. The other side of the SMC
material (20) had a glossy finish.
Example 4
[0233] In an example of a method according to the present
invention, a particulate substrate is positioned with a surface in
contact with a layer of sheet-form curable material, preferably
comprising SMC. In this example, the particulate substrate
comprises electromagnetic susceptor material such as gypsum or
graphite.
[0234] A weighted platen is placed on top of the SMC.
[0235] The substrate is irradiated with electromagnetic radiation
with a frequency of 2.45 GHz and a power of 800 W or 1000 W, for a
time period of 1 minute in a microwave oven.
[0236] The irradiation raises the temperature of the substrate to
approximately 200.degree. C., at which time the sheet-form curable
material begins to cure. During the initial curing phase the
sheet-form material flows into the interstitial spaces in the
particulate substrate. After the irradiation, the materials are
allowed to stand for around 3 minutes such that the sheet-form
material becomes fully cured.
[0237] Advantageously, this example demonstrates that the step of
applying pressure may be such that expensive hydraulic pressing
apparatus is not required, for example the pressing may be achieved
by simply placing a weight on top of the materials.
Example 5
[0238] The following example will be described with reference to
FIGS. 3 to 5.
[0239] On a lower part of a press, a template (31), wherein the
template is patterned in the form of masonry tiles was provided. In
particular, the template comprises raised portions (36) (see FIG.
4) which, in the final product, will result in mimicking of
grouting between masonry tiles in traditional brick walls.
[0240] A sheet of SMC material (32) was applied to the surface of
the template (31), and the sheet was extended so that it covered
the whole area of the template.
[0241] Masonry tiles (33) were subsequently positioned directly on
top of the sheet of SMC (32), such that the masonry tiles (33) were
positioned between the raised portions of the template (31).
[0242] A layer of particulate sand (34) to form the substrate was
applied on top of the arranged masonry tiles (33) and sheet of SMC
material (32). The sand used had a particle diameter of between 0.6
mm and 2.0 mm
[0243] An upper part of the press (35) was then onto the layers,
and a downward pressure of around 100 tonnes per m.sup.2 was
applied, such that the masonry tiles (33) and layer of sand (34)
were embedded into the sheet of SMC material (32) (see FIG. 5).
[0244] Once formed, the produced skin was removed from the
mould.
[0245] It will be appreciated that the present invention has been
described purely by way of example. Each feature disclosed in the
description, and (where appropriate) the claims and drawings may be
provided independently or in any appropriate combination. Thus it
will be appreciated that the various methods described herein could
be combined as appropriate to form a particular product.
* * * * *